The Evolution Of The Nobel Diesel Engine - Revision history

Toro Andersen at 18:47, 25 March 2026

2026-03-25T18:47:03Z

Toro Andersen at 18:32, 25 March 2026

2026-03-25T18:32:59Z

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 The fuel consumption og that engine at full load and normal speed vas 235 gr. pr b.h.p. hour.
-The weight of the engine complete with all accessories and flywheel was nine tons or 25,7 kg. (58 lbs.) per h.h.p. In order to test this engine under actual seagoing conditions, the engine was
+The weight of the engine complete with all accessories and flywheel was nine tons or 25,7 kg. (58 lbs.) per h.h.p. In order to test this engine under actual seagoing conditions, the engine was fitted into Mr. L. Nobel’s motor yacht ''Gradustchy.'' She was a boat of' 80 tons displacement, 120ft. length B.P., 13ft. breadth and 4ft. draught, and a speed of 13* knots. Exhaustive trials were carried out at sea with this boat in all sorts of weather, and the running’ of the engine proved quite satisfactory. However, the sea experience also showed that a complicated engine of that kind could be run only by very well trained engineers and was likely to give trouble in the hands of ordinary naval crews such a.s were then obtainable for submarines. Therefore this type of engine was abandoned and Nobels proceeded to design a. two-stroke submarine engine on a, modified principle. By 1911 the design of that new engine was ready and early in 1912 a two-cylinder experimental set was completed and ready for tests.
-fitted into Mr. L. Nobel’s motor yacht ''Gradustchy.'' She was a
+That experimental set had the two cylinders cast in block with separate cast iron liners. The two separate Cylinder heads were steel castings bolted to the cylinders (Fig. 35).
 The cylinder dimensions were: Diameter 450 m/m, by stroke 480 m/m, and it developed 450 b.h.p. at 320 r.p.m. In reality, this engine was a part, so to speak, of a six cylinder submarine engine of the same cylinder dimensions. The cylinders were mounted on a thin cast iron crankcase, and the tension stresses were taken up by through bolts anchored in the bedplate. The double acting scavenging pump, having a piston valve, and a three stage air compressor were direct driven from the forward tend of the crankshaft. The peculiarity of that engine was in the method of scavenging- it had the so-called controlled port scavenging, now adopted as standard by Nobels.
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 The lubrication of cylinders, gudgeon pins -and air compressor was forced by means of a mechanical lubricator, whereas the main bearings were gravity fed and big ends had centrifugal lubrication (banjo ring type). In order to study the reliability of this engine, it was put into the power station of Nobel Works in Petrograd in the summer of 1912, where it ran in parallel with ordinary stationary engines for five years.
-During the war years tliis engine was regularly running non-stop for six
+During the war years this engine was regularly running non-stop for six days a week.
-In summer 1917 the engine was removed from
+In summer 1917 the engine was removed from the power-house to the test shop again, rebuilt and further research work was carried out on it until the virtual closing of Nobel’s Russian Works in 1918. From the experience gained with that engine an 8-cylinder submarine engine was designed and a large number of such engines was built in 1914-1918, and fitted into all the large twin screw Russian submarines of the ''Kayuar'' class.
 These engines had four pairs of cylinders of diameter 390 m/m, by stroke 430 m/m. the pairs were cast en-bloc and had a common piston valve for the control of scavenging ports similar to those of the experimental engine (Fig. 36). The engines developed 1,360 b.h.p. at 350 r.p.m. The eleven throw crankshaft was supported in a cast iron bedplate. A cast iron crankcase acted as housing only because all the tensile stresses were taken up by through, bolts which supported the cylinders. The cylinder covers were steel castings and each cylinder had its own cover bolted to the cylinder block proper.
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 The ship, which originally was a passenger steamer and was converted to Diesel power, had the following leading dimensions: Length B.P. 243ft., breadth md. 34ft., depth md. 16ft. 9ins., and draught fully loaded 10 ft., displacement 1700 tons and cargo capacity 500 tons, speed 13 knots.
-There was accomoodation for 1000 passengers. Two four cylinder engines developed 600 b.h.p. each at a normal speed of 210 r.p.m.
+There was accomodation for 1000 passengers. Two four cylinder engines developed 600 b.h.p. each at a normal speed of 210 r.p.m.
 [[Category:Articles]]
 [[Category:Engines]]

Toro Andersen at 20:33, 24 March 2026

2026-03-24T20:33:52Z

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 The fuel consumption og that engine at full load and normal speed vas 235 gr. pr b.h.p. hour.
-The weight of the engine complete with all accessories and flywheel
+The weight of the engine complete with all accessories and flywheel was nine tons or 25,7 kg. (58 lbs.) per h.h.p. In order to test this engine under actual seagoing conditions, the engine was
 fitted into Mr. L. Nobel’s motor yacht ''Gradustchy.'' She was a
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 These engines had four pairs of cylinders of diameter 390 m/m, by stroke 430 m/m. the pairs were cast en-bloc and had a common piston valve for the control of scavenging ports similar to those of the experimental engine (Fig. 36). The engines developed 1,360 b.h.p. at 350 r.p.m. The eleven throw crankshaft was supported in a cast iron bedplate. A cast iron crankcase acted as housing only because all the tensile stresses were taken up by through, bolts which supported the cylinders. The cylinder covers were steel castings and each cylinder had its own cover bolted to the cylinder block proper.
-In general design it followed the experimental set although
+In general design it followed the experimental set although it differed from its details. The ports were of equal height. At the forward tend of the engine were placed two double acting scavenging pumps, the upper part of their trunk guides serving as the L.P. stage of' the air compressor. The remaining two stages (I.P. and H.P.) of the compressor were in tandem and driven from the very foremost crank.
-each propeller shaft at full speed would have had two engines
+The fuel valves were inelined ,so as to reduce the height of the engine. All the valves with the exception of safety valves were actuated by push rods and rockers from the camshaft, which was placed near the top of the crankcase. A centrifugal governor of the Jalms type acted as a cut out, and prevented racing of the engine. The first two engines were made reversible and they were fitted into the submarine ''"Kaguar".'' The remaining engines were non-reversible, as practice had shown that even with such large submarines the reverse motion could easily be given by the electromotors usually provided for underwater propulsion. All the control gear was at the reair end of the engine as is usual with submarine engines in general. A point of peculiar interest in connection with this engine is the method ,of lubrication. The cylinders gudgeon pins and air compressors were supplied with oil under pressure from mechanical lubricators, but the main bearings, which were water cooled, had ordinary gravity feed and the orankpins had centrifugal lubrication (banjo ring). No bearing trouble was experienced with this kind of lubrication in spite of the high speed of the engine and this only goes to prove, that with careful design such method of lubrication can be made as effective as the forced lubrication usually adopted for high speed engines. The fuel consumption of this engine at full load and normal speed was 228 gr. (0'504 lb.) per b.h.p.
-driving it, one directly and the other indirectly. This method
+The further development of submarine Nobel Diesel engines went in two ways: engines of higher power than the above and engines of lower power.
-of' propulsion was a modification of the Del-Proposto system.
+The lover power engines were of the six cylinder type with cylinders cast in pairs. They developed 550 b.h.p. at 350 r.p.m. The cylinder diameter was 300 m/m and stroke 400 m/m. The scavenging ports were controlled by horizontal rotary distributors mounted on a common shaft. Four such engines were to be placed in a submarine: two engines driving propellers direct (cruising condition) whereas the remaining two, coupled to dynamos, could charge the accumulators in the meantime, and supply additional power for full speed by driving the electromotors on the propeller shafts. Thus each propeller shaft at full speed would have had two engines driving it, one directly and the other indirectly. This method of propulsion was a modification of the Del-Proposto system.
 The larger engines were eight cylinders sets with cylinders cast separately and developing 2,500 b.h.p. at 250 r.p.m. These latter were of the cross-head type and were destined for the large Russian submarine twin-screw cruisers.
-Besides submarine engines, high power two-stroke auxiliary sets were built for the four .Russian battle cruisers of the ''Navarin'' class. Each ship was to have two such engines direct coupled to 320 K.W. dynamos. The engines developed 480 b.h.p. ,at 320 r.p.m. in six cylinders of 320 m/m diameter and 350 m/m stroke, they were of the crosshead type.
+Besides submarine engines, high power two-stroke auxiliary sets were built for the four Russian battle cruisers of the ''Navarin'' class. Each ship was to have two such engines direct coupled to 320 K.W. dynamos. The engines developed 480 b.h.p. ,at 320 r.p.m. in six cylinders of 320 m/m diameter and 350 m/m stroke, they were of the crosshead type.
 The cylinders were cast in pairs, with separate steel-casting heads for each cylinder. Each pair had a mechanically operated piston valve which controlled the inlet ports on the near side of the engine, while the air receiver or scavenging air pipe wais bolted to the off side of the engine above the exhaust pipe and communicated with the corresponding scavenging valve -by internal passages in the cylinder blocks. A double acting scavenging pump and three stage double tandem air compressor (intermediate stage was below the L.P. stage) were in line with the cylinders and direct driven from the forward end of crankshaft. The pistons were oil cooled, whereas the cylinders had sea water cooling.

Toro Andersen at 17:27, 24 March 2026

2026-03-24T17:27:25Z

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Toro Andersen: /* The Evolution of The Nobel Diesel Engine. (Part II.) */

2026-03-24T07:34:54Z

The Evolution of The Nobel Diesel Engine. (Part II.)

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Toro Andersen: /* Four-Stroke Nobel-Diesel Marine Engines. */

2026-03-24T07:08:14Z

Four-Stroke Nobel-Diesel Marine Engines.

← Older revision		Revision as of 07:08, 24 March 2026
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	The cylinder dimensions of that engine were: Diameter 600 m/m. and stroke 800 m/m. Three and four-cylinder sets of this size were built, developing 600 and 800 b.h.p. respectively. Two such 600 b.h.p. engines were installed in the steel rolling plant of '''Moscow Metal Works, Ltd'''., in 1907, one of these engines being direct coupled to the mills. Such work put very heavy stresses on the engine, as it had to work at a constantly variable load from practically 10% load to overload and ''vice versa.'' The fact that this engine has done this work already for fifteen years, only proves the reliability of the modern Diesel engine. Another interesting installation of an 800 b.h.p. engine was at the '''Tzaritzin Flour Mills'''. The engine was a four-cylinder set with a heavy flywheel pulley between the second and the third cylinders. The pulley was arranged for rope drive. The crankshaft was so designed that either pair of the cylinders could be uncoupled from the flywheel, the engine working then on two cylinders at lialf-power. The reason for such an arrangement was the doubt of the owners in the reliability of the Diesel engine, they preferring to have at least half the power than nothing at all in case of breakdown. It must be remembered that even a short stoppage of machinery in a flour mill entails considerable inconvenience and even loss to the millers, as most of the grain and flour in the middle of the process must he sent again from the start, and therefore the attitude of the Tzaritzin Mill owners was understandable, as to them at the time a Diesel engine installation was quite a novelty. However, it must be said to the credit of the builders of the engine that there never was an occasion to run the engine on two cylinders. Although the building of stationary Diesel engines formed a considerable branch of the Nobel Diesel business, it was for the designing and building of marine Diesel engines that Nobels spent most of their energies, and therefore the author will proceed to the description of a few interesting types of marine engines.		The cylinder dimensions of that engine were: Diameter 600 m/m. and stroke 800 m/m. Three and four-cylinder sets of this size were built, developing 600 and 800 b.h.p. respectively. Two such 600 b.h.p. engines were installed in the steel rolling plant of '''Moscow Metal Works, Ltd'''., in 1907, one of these engines being direct coupled to the mills. Such work put very heavy stresses on the engine, as it had to work at a constantly variable load from practically 10% load to overload and ''vice versa.'' The fact that this engine has done this work already for fifteen years, only proves the reliability of the modern Diesel engine. Another interesting installation of an 800 b.h.p. engine was at the '''Tzaritzin Flour Mills'''. The engine was a four-cylinder set with a heavy flywheel pulley between the second and the third cylinders. The pulley was arranged for rope drive. The crankshaft was so designed that either pair of the cylinders could be uncoupled from the flywheel, the engine working then on two cylinders at lialf-power. The reason for such an arrangement was the doubt of the owners in the reliability of the Diesel engine, they preferring to have at least half the power than nothing at all in case of breakdown. It must be remembered that even a short stoppage of machinery in a flour mill entails considerable inconvenience and even loss to the millers, as most of the grain and flour in the middle of the process must he sent again from the start, and therefore the attitude of the Tzaritzin Mill owners was understandable, as to them at the time a Diesel engine installation was quite a novelty. However, it must be said to the credit of the builders of the engine that there never was an occasion to run the engine on two cylinders. Although the building of stationary Diesel engines formed a considerable branch of the Nobel Diesel business, it was for the designing and building of marine Diesel engines that Nobels spent most of their energies, and therefore the author will proceed to the description of a few interesting types of marine engines.

	=== '''Four-Stroke Nobel-Diesel Marine Engines.''' ===		== '''Four-Stroke Nobel-Diesel Marine Engines.''' ==
	Not counting a small 20 b.h.p. French Diesel engine fitted into a small canal barge in France, it is to Nobels that belongs the credit of having built in 1903 the first marine Diesel engine and in which the speed could be varied by hand. That engine was a four-cylinder one of “A” frame trunk piston type and developed 180 b.h.p. at 240 r.p.m. The cylinder dimensions were: Diameter 320 m/m. and stroke 420 m/m. The outside view of the engine is shown in Fig. 2. Two such engines were fitted in 1904 into the motor-tank-ship "''Ssarmat''", of the Nobel Bros. Petroleum Co.		Not counting a small 20 b.h.p. French Diesel engine fitted into a small canal barge in France, it is to Nobels that belongs the credit of having built in 1903 the first marine Diesel engine and in which the speed could be varied by hand. That engine was a four-cylinder one of “A” frame trunk piston type and developed 180 b.h.p. at 240 r.p.m. The cylinder dimensions were: Diameter 320 m/m. and stroke 420 m/m. The outside view of the engine is shown in Fig. 2. Two such engines were fitted in 1904 into the motor-tank-ship "''Ssarmat''", of the Nobel Bros. Petroleum Co.

Toro Andersen at 20:54, 23 March 2026

2026-03-23T20:54:21Z

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Toro Andersen at 19:26, 23 March 2026

2026-03-23T19:26:16Z

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Toro Andersen at 15:40, 23 March 2026

2026-03-23T15:40:03Z

← Older revision		Revision as of 15:40, 23 March 2026
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	[[File:Nobel Diesel Fig 41.png\|alt=Nobel Diesel Fig 41\|thumb\|Fig. 41. View showing relative position of Nobel Diesel Engines in Motorship “ Imperatritza Alexandra”]]		[[File:Nobel Diesel Fig 41.png\|alt=Nobel Diesel Fig 41\|thumb\|Fig. 41. View showing relative position of Nobel Diesel Engines in Motorship “ Imperatritza Alexandra”]]
	[[File:Nobel Diesel Fig 42.png\|alt=Nobel Diesel Fig 42\|thumb\|Fig. 42, 1600 B.H.P. Nobel Diesel Two-stroke Marine Engine.]]		[[File:Nobel Diesel Fig 42.png\|alt=Nobel Diesel Fig 42\|thumb\|Fig. 42, 1600 B.H.P. Nobel Diesel Two-stroke Marine Engine.]]
			[[File:Nobel Diesel Fig 43.png\|alt=Nobel Diesel Fig 43\|thumb\|Nobel Diesel Fig 43]]

	== '''Nobel Diesel''' ==		== '''Nobel Diesel''' ==

Toro Andersen at 15:39, 23 March 2026

2026-03-23T15:39:26Z

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← Older revision		Revision as of 18:47, 25 March 2026
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	Among the sea-going motor tankships can he mentioned Motorship ''"Robert Nobel",'' of Nobel Bros. Petroleum Co. (Fig. 13. She was originally a twin-screw tank steamer of 1,700 D.AV. capacity (L. 260ft., B. 34ft., D. 17ft., draught 14ft.) In 1909 she was to undergo a complete overhaul of engines and boilers, but instead of that it was decided to convert her into a motorship.		Among the sea-going motor tankships can he mentioned Motorship ''"Robert Nobel",'' of Nobel Bros. Petroleum Co. (Fig. 13. She was originally a twin-screw tank steamer of 1,700 D.AV. capacity (L. 260ft., B. 34ft., D. 17ft., draught 14ft.) In 1909 she was to undergo a complete overhaul of engines and boilers, but instead of that it was decided to convert her into a motorship.

	Two four-cylinder Nobel-Diesel engines of the enclosed crankcase type of 400 b.h.p. each were fitted in 1910, driving propeller shafts through Dohmen Leblanc clutches at 215 r.p.m. The engines had the following cylinder dimensions: diameter 450 mm and stroke 510 mm. and were direct reversible. The reverse gear, however, was different from Carlsund’s gear used on the smaller power engines, as it consisted of two set of rollers on the links of valve rocking levers.		Two four-cylinder '''Nobel-Diesel''' engines of the enclosed crankcase type of 400 b.h.p. each were fitted in 1910, driving propeller shafts through Dohmen Leblanc clutches at 215 r.p.m. The engines had the following cylinder dimensions: diameter 450 mm and stroke 510 mm. and were direct reversible. The reverse gear, however, was different from Carlsund’s gear used on the smaller power engines, as it consisted of two set of rollers on the links of valve rocking levers.


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	The reason for the change of design in the reverse gear was that at the time it was considered that the shifting of cams by hand could only be performed on engines of comparatively small powers, and that in larger sizes it would be beyond the power of an ordinary man to shift the cams and thus a servo motor would have to be introduced.		The reason for the change of design in the reverse gear was that at the time it was considered that the shifting of cams by hand could only be performed on engines of comparatively small powers, and that in larger sizes it would be beyond the power of an ordinary man to shift the cams and thus a servo motor would have to be introduced.

	The Nordstroem’s double roller reverse gear was so designed as to abolish the cam shifting and the whole of the reversing operation could be performed in 7-8 seconds. The idea about the impossibility of cam shifting by hand on large engines proved, however, to be false, and it will be shown later that all modern two-stroke Nobel-Diesel engines up to the very largest powers have hand camshifting, without the use of any servo motors whatever.		The Nordstroem’s double roller reverse gear was so designed as to abolish the cam shifting and the whole of the reversing operation could be performed in 7-8 seconds. The idea about the impossibility of cam shifting by hand on large engines proved, however, to be false, and it will be shown later that all modern two-stroke '''Nobel-Diesel''' engines up to the very largest powers have hand camshifting, without the use of any servo motors whatever.

	This Nordstroem’s double roller reverse gear, though not used at present by Nobels, has been revived lately by a well-known Swiss concern on their two-stroke engines.		This Nordstroem’s double roller reverse gear, though not used at present by Nobels, has been revived lately by a well-known Swiss concern on their two-stroke engines.
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	These fourteen submarines were of three different types and sizes: ''Ssom'' class, six boats of Lake type of 110 tons displacement had petrol engines of 160 b.h.p.: ''Makrel'' class, seven boats of Holland type, and 115 tons displacement, with engines of 120 b.h.p. and the ''Delphin'' class (one boat) was of Russian design with petrol engines of 200 b.h.p. Therefore, owing to the difference in size and shape of engine room, three entirely different types of engines had to be produced.		These fourteen submarines were of three different types and sizes: ''Ssom'' class, six boats of Lake type of 110 tons displacement had petrol engines of 160 b.h.p.: ''Makrel'' class, seven boats of Holland type, and 115 tons displacement, with engines of 120 b.h.p. and the ''Delphin'' class (one boat) was of Russian design with petrol engines of 200 b.h.p. Therefore, owing to the difference in size and shape of engine room, three entirely different types of engines had to be produced.

	The conversion began in 1910 with the Lake type boats first, and instead of the old petrol engine was installed in each boat one six-cylinder 160 b.h.p. non-reversible Nobel-Diesel engine, giving the boat a surface speed of 9½ knots. In general appearance these engines resembled also very much the present-day aero engines, as can be seen from Figs. 20 and 21.		The conversion began in 1910 with the Lake type boats first, and instead of the old petrol engine was installed in each boat one six-cylinder 160 b.h.p. non-reversible '''Nobel-Diesel''' engine, giving the boat a surface speed of 9½ knots. In general appearance these engines resembled also very much the present-day aero engines, as can be seen from Figs. 20 and 21.

	The cylinder dimensions were: diameter 225 m/m and stroke 300 mm, and the engine developed its full power of 160 b.h.p. at 440 r.p.m. The weight of the engine was only 2,900 kg. (6,400 lbs.), which worked out at 18,1 kg per b.h.p. In order to get such light weight combined with necessary strength and stiffness, the usual orthodox design of Diesel engines had to be departed from, and the engine designed on entirely novel lines.		The cylinder dimensions were: diameter 225 m/m and stroke 300 mm, and the engine developed its full power of 160 b.h.p. at 440 r.p.m. The weight of the engine was only 2,900 kg. (6,400 lbs.), which worked out at 18,1 kg per b.h.p. In order to get such light weight combined with necessary strength and stiffness, the usual orthodox design of Diesel engines had to be departed from, and the engine designed on entirely novel lines.
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	The higher maximum pressures are detrimental to the smooth running of an engine and require therefore special design of engine in order to withstand the high stresses set up, and this entails a bulkier and heavier engine. '''Mr. Windeler''' mentioned the slow running and manoeuvring capabilities of the Doxford engine, which being of the opposed piston type of four units is, in reality, an eight piston engine having eight cranks, therefore, it may be considered as an eight cylinder single acting engine. The two outside cranks of each unit, belonging to the upper piston can be reckoned as one crank as far as the turning moment is concerned. The engine in question runs normally at 75-77 revs. per min., and a minimum speed of 15-17 r.p.m. was obtained at sea.		The higher maximum pressures are detrimental to the smooth running of an engine and require therefore special design of engine in order to withstand the high stresses set up, and this entails a bulkier and heavier engine. '''Mr. Windeler''' mentioned the slow running and manoeuvring capabilities of the Doxford engine, which being of the opposed piston type of four units is, in reality, an eight piston engine having eight cranks, therefore, it may be considered as an eight cylinder single acting engine. The two outside cranks of each unit, belonging to the upper piston can be reckoned as one crank as far as the turning moment is concerned. The engine in question runs normally at 75-77 revs. per min., and a minimum speed of 15-17 r.p.m. was obtained at sea.

	This is a remarkably low speed, as it is only about 20% of the normal speed. The Nobel-Diesel two-stroke single acting four-cylinder engine of 1600 B.H.P. can run at 24% of normal speed without any difficulty whatever.		This is a remarkably low speed, as it is only about 20% of the normal speed. The '''Nobel-Diesel''' two-stroke single acting four-cylinder engine of 1600 B.H.P. can run at 24% of normal speed without any difficulty whatever.

	I would like to thank Mr. McLaren for his kind remarks. The next speaker spoke about weights. I presume he meant weight per H.P. Through suitable design the weight per B.H.P. can be reduced considerably, as is instanced for example by the Nobel-Diesel 200 B.H.P. V-type engine of the M.Y. ''"Intermezzo".'' I do not think any engines of the high compression type have been built lighter than the above. I understand that the aviation people are now beginning seriously to consider the application of Diesel engines for aeroplanes and airships on account of greater safety when using oil fuel.		I would like to thank Mr. McLaren for his kind remarks. The next speaker spoke about weights. I presume he meant weight per H.P. Through suitable design the weight per B.H.P. can be reduced considerably, as is instanced for example by the '''Nobel-Diesel''' 200 B.H.P. V-type engine of the M.Y. ''"Intermezzo".'' I do not think any engines of the high compression type have been built lighter than the above. I understand that the aviation people are now beginning seriously to consider the application of Diesel engines for aeroplanes and airships on account of greater safety when using oil fuel.

	I have heard recently that a firm in Scotland is experimenting with a very light high speed Diesel engine intended for aviation purposes, though for obvious reasons, further particulars of the above engine are not yet available for the technical press. Regarding these light weight engines, one cannot expect them to run continuously at full load at the high speeds for which they are necessarily designed. It is not feasible for instance to aim at a reduction in weight of an engine for the mercantile marine on the scale of an engine to be used in a submarine. Rigidity and reliability have to be taken into account as well as low speed to suit the propeller in case of merchant ships.		I have heard recently that a firm in Scotland is experimenting with a very light high speed Diesel engine intended for aviation purposes, though for obvious reasons, further particulars of the above engine are not yet available for the technical press. Regarding these light weight engines, one cannot expect them to run continuously at full load at the high speeds for which they are necessarily designed. It is not feasible for instance to aim at a reduction in weight of an engine for the mercantile marine on the scale of an engine to be used in a submarine. Rigidity and reliability have to be taken into account as well as low speed to suit the propeller in case of merchant ships.
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	Regarding Mr. Thom’s remarks about the slow running of steam engines I do think that the Diesel engine can compete with the steam engine in this respect, because speeds of 20-25 r.p.m. are about the slowest speeds one gets with condensing steam engines driving their own vacuum pumps and these speeds are those of Diesels also. I do not know the particular reason why a fuel injection pressure of over 9000 lbs. per sq. in. had been adopted in the Doxford engine, but other makers of solid injection engines use for marine work injection pressures of 2500-3000 lbs. per sq. in. (mercantile type) and 4000-6000 lbs. per sq. in. (submarine type).		Regarding Mr. Thom’s remarks about the slow running of steam engines I do think that the Diesel engine can compete with the steam engine in this respect, because speeds of 20-25 r.p.m. are about the slowest speeds one gets with condensing steam engines driving their own vacuum pumps and these speeds are those of Diesels also. I do not know the particular reason why a fuel injection pressure of over 9000 lbs. per sq. in. had been adopted in the Doxford engine, but other makers of solid injection engines use for marine work injection pressures of 2500-3000 lbs. per sq. in. (mercantile type) and 4000-6000 lbs. per sq. in. (submarine type).

	As the Doxford engine runs at 77 r.p.m. only, it scarcely could be called a high speed engine. I think high injection pressures that are now used are an attempt to obtain a better atomisation of the fuel, and, as the problem of solid injection is still in its infancy, naturally a great variety of systems are being tried in the endeavour to obtain satisfactory working results. With regard to relative space required by the engine room in a motor ship and a steam ship, I consider it unfair to compare the former with the latter on hull dimensions.		As the [[Doxford]] engine runs at 77 r.p.m. only, it scarcely could be called a high speed engine. I think high injection pressures that are now used are an attempt to obtain a better atomisation of the fuel, and, as the problem of solid injection is still in its infancy, naturally a great variety of systems are being tried in the endeavour to obtain satisfactory working results. With regard to relative space required by the engine room in a motor ship and a steam ship, I consider it unfair to compare the former with the latter on hull dimensions.

	If one puts into two sister hulls steam machinery in one and Diesels (especially two-stroke) in the other, the two ships will have still practically the same D.W. capacity because their engine rooms will have to be equal for reasons explained by Mr. Fielden. This will mean that in case of the motorship there will be plenty of spare space in the engine room which will not be available for cargo. When designing a motorship as such, which is to compete with the steamer of same D.W. capacity, the hull of the motorship can be made much smaller. The 13% engine room space can thus be esaily obtained, giving in the same time an engine room of ample but not excessive dimensions.		If one puts into two sister hulls steam machinery in one and Diesels (especially two-stroke) in the other, the two ships will have still practically the same D.W. capacity because their engine rooms will have to be equal for reasons explained by Mr. Fielden. This will mean that in case of the motorship there will be plenty of spare space in the engine room which will not be available for cargo. When designing a motorship as such, which is to compete with the steamer of same D.W. capacity, the hull of the motorship can be made much smaller. The 13% engine room space can thus be esaily obtained, giving in the same time an engine room of ample but not excessive dimensions.